A working machine generally comprises a working arm and an attachment connected thereto. The working machine may be in the form of a materials handling vehicle such as a loading shovel, telescopic handler, an excavator, a backhoe loader, etc., with an attachment in the form of a shovel, bucket or forks, etc. connected thereto.
The working machine generally also comprises an operator compartment structure, often referred to as a “cab”, which is designed to protect a user under certain conditions.
The operator compartment structure may be in the form of a roll over protection structure (ROPS) which is intended to protect a user from injuries caused by the working vehicle overturning or rolling over; in the form of a falling object protective structure (FOPS) which is intended to protect a user from injuries caused by falling objects; or both an ROPS and FOPS compliant structure.
In working machines, the operator compartment structure is generally positioned proximate the engine of the working machine, and as a result the environment within the compartment structure can be quite noisy and become uncomfortable for a user after a prolonged amount of time.
A known way of trying to reduce the noise level within the compartment structure due to engine noise, is by having the compartment structure enclosed by panels in order to reduce the amount of external noise from the engine entering the compartment structure. Depending on the required visibility and direction of visibility by the user, the panels may be see through (transparent), non-see through (non-transparent) or a combination of see through and non-see through panels may be utilized to enclose the compartment structure.
However, increases in the power of an engine may result in an increase in the noise generated, which reduces the effect the panels enclosing the compartment structure have in attenuating the noise heard within the compartment structure.
Increasing the thickness of the panels will help reduce the engine noise heard within the compartment structure but this will have the adverse effect of increasing production costs.
In some cases, it is known to incorporate liners within the compartment structure which are adapted to reduce the amount of engine noise entering the compartment structure.
However, under certain conditions, a standing wave will be generated within the compartment structure which exacerbates the noise within the compartment structure and the liners and/or panels have been shown to have no or limited effect on the issues caused by the generation of a standing wave within the compartment structure.
In addition, additional noise can be generated as a result of vibrations from the engine, causing parts of the compartment structure, such as the roof, to oscillate and generate additional noise within the compartment structure. The use of liners and/or panels have been shown to have no or limited effect in reducing the generation of additional noise within the compartment structure due to vibrations.
It is desirable to provide an operator compartment structure for a working machine which addresses one or more of the problems and disadvantages identified above.